The present invention relates to a combustion device, and in particular relates to a combustion device in which a check valve is connected to an exhaust port, in order for the exhaust port to be connected to an exhaust duct that is utilized in common by a plurality of combustion devices.
In the prior art, a compound combustion device is per se known in which a plurality of combustion devices each of which comprises individual combustion unit and individual blower fan are installed in a facility in parallel, and the exhaust ports of these combustion devices are all connected to a common exhaust duct. With such a compound combustion device, operation is performed to discharge the combustion exhaust from each of the combustion devices to the exterior of the facility via the common exhaust duct by rotating the respective blower fan, while adjusting the number of operating combustion devices according to the load.
However, if only some of the combustion devices among the plurality of combustion devices are being operated to perform combustion, then, since the blower fans of the combustion devices that are in the non-combusting state are not being rotated, accordingly the combustion exhaust may flow in reverse from the common exhaust duct into the exhaust ports of one or more of the combustion devices that are in the non-combusting state, and there is a fear that this reverse flow may penetrate into the interior of the facility.
Accordingly, as shown in the Prior Art Document, normally, check valves are connected so that no reverse flows of exhaust back from the common exhaust duct into the exhaust ports of the combustion devices can occur.
Since the check valve disclosed in the Prior Art Document incorporates both a large sized first valve and also a compact second valve which is provided in the center portion of this first valve, accordingly when the amount of combustion exhaust is small only the second valve is opened, and when the amount of combustion exhaust increases the first valve is also opened.
As shown in FIG. 2 which relates to an embodiment of the present invention, the check valve that the present applicant employs comprises a circular plate shaped valve plate 26, four guide rods 27 that guide this valve plate 26 so that it can move upward and downward freely, and a horizontal stopper 28 that is fixed to the upper end portions of these four guide rods 27. When the rotation of the blower fan starts during air purge directly before combustion operation, the valve plate 26 rises and exhaust is discharged.
Japanese Patent 5,852,458 is cited as the Prior Art Document.
When a check valve as shown in FIG. 2 is employed, during air purge (i.e. pre-purging) when the combustion device is ignited and when the blower fan is rotationally driven at a high acceleration in order to reach its predetermined rated rotational speed in a short time interval of the order of one second, the valve plate 26 of the above described check valve rises sharply and collides with the stopper 28, so that there is the problem that an abrupt and unpleasant clattering noise is generated.
The object of the present invention is to provide a combustion device, with which it is arranged for no abrupt noise to be generated by a check valve of the above type during such air purge.